Probiotic microorganisms comprise living or viable cells, which, in their living form, show advantageous effects in human or animal bodies. Probiotic compositions contain such microorganisms. Advantageous effects may in particular be the improvement of the microflora of the digestive tract. In particular, undesired other microorganisms can be inhibited in the microflora by immediate interactions between the probiotic microorganisms and the undesired microorganisms, by immediate interactions due to inhibitions of the metabolism of the undesired microorganism by expression products of the probiotic microorganism, or by intensification of the natural immune system. In general, it is assumed that a main mechanism is the competitive settlement of the gastrointestinal tract, whereby undesired microorganisms cannot settle anymore on the mucosa to a disturbing extent or are displaced.
A group of probiotic microorganisms is for instance formed by Lactobacillus strains. These are typically gram-positive, microaerophilic or anaerobic bacteria fermenting sugar with the generation of acids, in particular of lactic acid.
From the document U.S. Pat. No. 5,716,615, a pharmaceutical composition is known in the art, which amongst others contains Lactobacilli. This pharmaceutical composition can be used, amongst others, for the treatment of diseases of the gastrointestinal tract.
From the document US 2005/0186190 A1, a dietetic or pharmaceutical composition is known in the art, which contains sphingomyelinase or lactobacilli containing sphingomyelinase. This composition is suitable for treatments of infections with Heliobacter pylori. 
From the document WO 2004/087891, Lactobacillus strains are known in the art, which are suitable for the production of pharmaceutical or dietetic compositions for the treatment of infections of the gastrointestinal tract with Helicobacter pylori. 
From the document WO 2005/060937 A1, tablet-shaped formulations are known in the art, which contain viable Lactobacillus cells. These are suitable for the oral administration and treatment of infections of the gastrointestinal tract with pathogens.
From the document WO 2004/031368 A1, Lactobacillus strains are known in the art, which are suitable for the treatment of inflammations, which are associated with an infection with Helicobacter pylori. 
Interactions of lactobacilli with Helicobacter pylori are further known in the art from the documents Wang et al., Am. J. Clin. Nutr. 80:737-41 (2004); Felley et al., Best Practice & Research Clinical Gastroenterology 17(5):785-791 (2003); Cazzato et al., Scandinavian Journal of Nutrition 48(1):26-31 (2004); and Sgouras et al., Applied and Environmental Microbiology 70(1):518-526 (2004).
Helicobacter pylori is a spiral-shaped bacterium colonizing the stomach, and by means of production of urease the pH value in the stomach is increased, and thus the bacteria are protected against the stomach acid. The bacteria penetrate the mucosa and deposit at epithelial cells of the stomach. Such an infection activates the body-own immune system, but the immune response is not sufficiently effective for eliminating the infection, with the consequence of an intensifying immune response. Finally, a chronic inflammation and illness with gastritis or stomach ulcers will occur. Up to now, it is not yet known, by means of which mechanisms Helicobacter pylori resists to the immune system.
About the effective mechanisms of the prior art Lactobacillus strains against Helicobacter pylori, various theories are presented in the above documents. Safe findings about the mechanisms do not exist, however.
Overall, it is desirable to develop Lactobacillus strains, which keep the Helicobacter pylori cell count in the stomach very low, and which are otherwise free from physiological side effects.